A ring binder mechanism includes ring members for retaining loose-leaf pages, such as hole-punched pages, in a file or notebook. The ring members may be selectively opened to add or remove pages or closed to retain pages while allowing the pages to be moved along the ring members. Typically, the ring members mount on two adjacent hinge plates that join together about a pivot axis. An elongate housing loosely supports the hinge plates within the housing and holds the hinge plates together so they may pivot relative to the housing.
The undeformed housing is slightly narrower than the joined hinge plates when the hinge plates are in a coplanar position (180°). As the hinge plates pivot through this position, they deform the resilient housing and cause a spring force in the housing that urges the hinge plates to pivot away from the coplanar position, either opening or closing the ring members. Thus, when the ring members are closed the spring force resists hinge plate movement and clamps the ring members together. Similarly, when the ring members are open, the spring force holds them apart. An operator may overcome this force by manually pulling the ring members apart or pushing them together. Levers can also be provided on one or both ends of the housing for actuating the ring members between the open and closed positions.
A drawback to typical ring binder mechanism configurations is that when the ring members are closed, they do not inhibit unintended separating of the ring members, such as if the mechanism is accidentally dropped. There is a need, therefore, for a blocking device that is capable of blocking all of the ring members of a ring binder mechanism closed that is inexpensive to manufacture, simple to construct, easy to use, and reliable in repeated operation.